Copper base alloy

ABSTRACT

A copper base alloy having a combination of strength and electrical conductivity which make it a suitable replacement for the C.D.A. 400 series tin brasses. The alloy contains from about 0.5 to about 2.8 percent iron and, preferably, from about 1.0 to about 2.0 percent iron; from about 0.2 to about 2.0 percent cobalt and, preferably, from about 0.3 to about 1.0% cobalt; from about 5 to about 15 percent zinc and, preferably, from about 7 to about 13 percent zinc; provided that the sum of the iron plus cobalt should be from about 0.8 to about 3.0 percent and, preferably, from about 1.5 to about 2.5 percent.

' [22] Filed:

United States Patent [191 Crane et al.

1 COPPER BASE ALLOY [73] Assignee: Olin Corporation, New Haven,

Conn.

July 3, 1972 [21] Appl. No.: 268,485

[52] U.S. Cl. 75/l57.5, 75/153 [51] Int. Cl. C22c 9/06, C22c 9/04 [58] Field of Search 75/153, 157.5

[56] References Cited UNITED STATES PATENTS 1,723,922 8/1929 Corson 75/153 X 1,959,509 5/1934 Tour 75/l57.5

2,126,827 8/1938 Smith.... 75/157.5 X 2,147,844 2/1939 Kelly 75/153 June 11, 1974 8/1939 Kelly 75/l57.5 X 9/1942 Mitchell 75/l57.5

[ 5 7 ABSTRACT A copper base alloy having a combination of strength and electrical conductivity which make it a suitable replacement for the C.D.A. 400 series tin brasses. The alloy contains from about 0.5 to about 2.8 percent iron and, preferably, from about 1.0 to about 2.0 percent iron; from about 0.2 to about 2.0 percent cobalt and, preferably, from about 0.3 to about 1.0% cobalt; from about 5 to about 15 percent zinc and, preferably, from about 7 to about 13 percent zinc; provided that the sum of the iron plus cobalt should be from about 0.8 to about 3.0 percent and, preferably, from about 1.5 to about 2.5 percent.

6 Claims, No Drawings 1 COPPER BASE ALLOY BACKGROUND OF THE INVENTION This invention provides a novel alloy which has a combination of strength and electrical conductivity which make it suitable for use in structural electrical components. The alloys possess sufficient ductility to be formed into intricate parts such as electrical receptacles. Since such parts are used in a variety of environments and are in a highly stressed condition, stress corrosion resistance is highly important.

Tin brasses, namely, the C.D.A. 400 series alloys are commonly used for this type of application since they combine the above described properties. In general, the electrical conductivity of these 400 series alloys range from 28 percent IACS for C.D.A. Alloy 425 which is the strongest of the series to 41 percent IACS for C.D.A. Alloy 405 which possesses the lowest strength of the series. Various of these alloys particularly those containing higher tin concentrations are difficult to manufacture, particularly with regard to casting and hot rollability.

SUMMARY OF THE INVENTION In accordance with this invention, a copper base alloy is provided containing from about 0.5 to about 2.8 percent iron and, preferably, from about 1.0 to about 2.0 percentiron; from about 0.2 to about 2.0 percent cobalt and, preferably, from about 0.3 to about 1.0 percent cobalt; from about 5 to about percent zinc and, preferably, from about 7 to about 13 percent zinc; provided that the sum of the iron plus cobalt should be from about 0.8 to about 3.0 percent, and, preferably, from about 1.5 to about 2.5 percent.

The aforenoted novel alloys provide electrical conductivity that is superior to those of the 400 series tin brasses at a comparable strength to limiting bend radius ratio; or at comparable conductivity, they provide superior strength to limiting bend radius ratio.

Accordingly, it is a principal object of this invention to provide a copper base alloy containing iron, cobalt and zinc within specific ranges which provide an improved combination of strength and electrical conductivity.

It is a further object of this invention to provide cop- 'per base alloysas above which have improved abrasion resistance as compared to the tin brasses and comparable or better stress corrosion resistance.

Other objects and advantages will become apparent to those skilled in the art from the detailed description which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention, copper base alloys are provided having an electrical conductivity that is superior to that of the tin brasses at a comparable strength or at comparable conductivity, they provide superior strength.

The copper base alloys in accordance with this invention contain about 0.5 to about 2.8 percent iron, about 0.2 to about 2.0 percent cobalt, about 5 to about 15 percent zinc, balance copper, provided that the sum of the iron plus cobalt contents is from about 0.8 to about 3.0 percent. Preferably, the alloys in'accordance with this invention consist essentially of about 1.0 to about 2.0 percent iron, about 0.3 to about 1.0 percent cobalt,

about 7 to about 13 percent zinc, balance copper, provided that the sum of the iron plus cobalt contents is from about 1.5 to about 2.5 percent. Impurities may be present in amounts which do not adversely affect the properties of the inventive alloys.

Impurities at the following levels separately or in combination cause no deleterious effect on the casting or hot and cold rolling characteristics of the alloy of this invention: phosphorus less than about 0.03 percent, lead less than about-0.03 percent, tin less than about 0.05 percent, nickel less than about 0.05 percent, manganese less than about 0.10 percent, aluminum less than about 0.10 percent, silver less than about 0.05 percent and silicon less than about 0.10 percent. It is preferred that the maximum. total impurities be limited to less than 0.2 percent to minimize adverse affects on the properties of the alloys.

It has been found in accordance with this invention that when cobalt is added to a copper base-iron-zinc alloy, a synergistic improvement in strength properties is obtained, namely, a copper base-iron-zinc-cobalt alloy within the ranges of this invention has been found to have a markedly improved tensile strength as compared to a copper base-iron-zinc alloy without cobalt but having an iron content substantially equal to the sum of the iron and cobalt contents in the alloy of this invention.

If the maximum limits for the sum of the iron plus cobalt contents are exceeded, segregation of the ironand-cobalt-rich phases detracts from'the mechanical properties and ease of processing. The preferred limit for iron plus cobalt was established at 2.5 percent. The minimum limit for the sum of the iron and cobalt contents is the amount necessary to achieve desirable mechanical properties.

The maximum zinc content was established on the basis of stress corrosion resistance. The minimum zinc content is based on the necessity to achieve desired mechanical properties.

It has also been found that phosphorus has a detrimental effect on stress corrosion life of the inventive alloy and on the bend properties of .the alloy. Therefore, the phosphorus content should be minimized and preferably should not exceed 0.02 percent.

The alloys in accordance with this invention may be prepared in accordance with the following practice.

Melting and Casting: Melt the copper, add the iron and cobalt, heat to 1,300C, and hold until the iron and cobalt are thoroughly dissolved, reduce the temperature to 1,200C and add the zinc. Cast at a temperature high enough to assure minimum mold temperature of l,lC. Other casting parameters are in accordance with conventional practice in the art.

Hot Rolling: Soak at a temperature of about 915 to about 975C; soak time and pass schedule may be set as desired; last pass temperature preferably should be above 500C.

Cold Rolling: The alloys of this invention have better than 75 percent cold rollability after hot rolling above 500C or after interannealing. A minimum of 50 percent cold reduction prior to annealing is preferred.

Annealing: Annealing for softening can be performed either by bell annealing or strip annealing. The choice of bell annealing versus strip annealing is predicated upon desired electrical conductivity. Where maximum conductivity is required, bell annealing is preferred.

1t is preferred in accordance with this invention in order to maintain the improved strength in the annealed and cold worked conditions that interanneals and the final anneal during the cold working be carried out in the range of 400 to 600C.

The alloy may be cleaned by conventional procedures and it has been found that standard sulfuric acid cleaning is acceptable.

Accordingly, it should be apparent that the alloy in accordance with this invention may be readily fabri- Cated without the difficulty encountered with the tin brasses. Further, the alloy is readily joinable by soldering and it should tin, nickel or chrome plate as well as tin brasses. The alloyv shows unusually good wear resistance as compared to C.D.A. Alloy 411 as well as C.D.A. Alloy 425. This may make it suitable for bearing applications for which Alloy 41 l is now used.

The invention will now be more fully illustrated by reference to the following examples.

EXAMPLE l A series of alloys in accordance with this invention were prepared as follows.

ALLOYS (Composition in wt.%)

Known data for C.D.A. Alloys 405, 41 l, 422 and 425, which alloys are denoted as Alloys D, E, F and G, are presented for comparison.

ALLOYS (Composition in wt./r)

CDA

Sn Zn Cu Alloy D 0.7-1.3 2.7-5.3 Bal. 405 E 0.8-1.4 0.6-13.2 Bal. 422 F 1.5-3 7-1 1.5 Ba]. 425 G 0.3-0.7 7.3-10.7 Bal. 411

Alloys A, B and C representing the alloys of the invention were processed by melting at 1,300C and Durville casting at a temperature of 1,175C; hot rolling from a thickness of 1% inches to approximately 0.5 inch at a starting temperature of 950C and a finishing temperature of about 600C; surface milling to produce a clean surface; cold rolling to 0.080 inch gage for Alloys A and B and 0.060 inch for Alloy C; annealing at 500C for hours for Alloys A and B and at 500C for 16 hours for Alloy C; then cold rolling to various reductions.

The tensile strength, electrical conductivity and limiting bend radii are shown in Tables I and I1 below. The properties are compared with Alloys D, E, F and G which are commercial tin brasses.

4 E .040" 86 3 16 A .030" 91 2 5 D .030" 81 4 7 E .030" 86 3 12 B .040" 93 4 10 E .040" 92' 4 16 F .040" 94 3 12 C .025" 82 t6 2 1) .025" 81 4 6 TABLE ll ANNEALED ELECTRICAL CONDUCTlVlTY Alloy lACS strength. bend and electrical conductivity of Alloys D.E.F.G. taken from data sheets for typical alloys within the C.D.A. Alloy rangcs.

The data tabulated above clearly establishes that the novel alloys in accordance with this invention provide superior electrical conductivity to those of the 400 series tin brasses at comparable strength to limiting bend radius ratio; or at a comparable conductivity, they provide superior strength to limiting bend radius ratio.

The data for Alloys A, B and C demonstrate the tradeoff between conductivity and strength as the zinc content is lowered; however, the alloy of this invention Alloy C, maintains comparable strength to C.D.A.

Alloy 405, Alloy D, while attaining a higher conductiv- EXAMPLE 11 A series of alloys in accordance with this invention were prepared in a manner similar to that set forth in Example I, The compositions of the alloys so prepared were as follows.

ALLOYS (Composition in wt.

The tensile and yield strengths and electrical conductivity in the annealed condition are presented in Table 111 below. Table 111 further gives these strengths of the alloys after cold rolling 30 and 50 percent from the 0.080 inch gage.

TABLE III ANNEALED 500 C ANNEALED 500C ANNEALED 500 C COLD ROLLED Alloy (KSI) (KSl) (71lAXSJ (KSI) (KSl) (KSI) (KS!) H 62 43 34 86 81 90 87 O 66 34 88 83 95 88 J 65 49 33 88 83 94 '88 K 64 48 33 88 82 94 87 The data tabulated above clearly establish that the improved properties of the alloys of this invention are obtained over a wide range of cobalt contents and iron plus cobalt contents. The data further establish that the alloys of this invention can obtain in the annealed condition an ultimate tensile strength of at least 60 ksi and, preferably, at least 62 ksi and an electrical conductivity of at least 33 percent IACS. Further, in the 30 percent annealed and cold rolled condition the alloys. can obtain a tensile strength of at least 86 ksi and in the annealed and cold rolled 50 percent condition, they can obtain a tensile strength of at least 93 ksi.

EXAMPLE lll Samples of Alloys A and B from Example I and of Alloys E and F were subjected to accelerated stress corrosion testing in environments of moist ammonia and Mattsson's pH 7.2 solution. The data obtained from this test are shown in Table IV below.

TABLE IV TIME TO FAILURE, HRS.

Mattssons Moist Alloy pH 7.2 Sol. Ammonia A (l) 90 B (l) 13 E (l) F (1) 61 (1) No failure after. 2..h9 1. s- T.esttennina.ted.....

The alloys of this invention have particular application in structural electrical components such as electrical contacts, electrical receptacles, electrical connectors and the like.

All of the compositions specified in this application by percentage are given in percentage by weight.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

l. A copper base alloy consisting essentially of about 0.5 to about 2.8 percent iron, about 0.2 to about 2.0 percent cobalt, about 5 to about 15 percent zinc, and the balance copper, provided that the sum of the iron plus cobalt contents shall be from about 0.8 to about 3.0 percent.

2. A copper base alloy as in claim 1 consisting essentially of about 1.0 to about 2.0 percent iron, about 0.3 to about 1.0 percent cobalt, about 7 to about 13 percent zinc, and the balance copper, provided that the sum of the iron plus cobalt contents shall be from about 1.5 to about 2.5 percent.

3. A copper base alloy as in claim 2 containing less than 0.03 percent phosphorus.

4. A copper base alloy as in claim 2 wherein said alloy is in the annealed condition.

5. A copper base alloy as in claim 2 wherein said alloy is in the annealed and cold worked condition.

6. A copper base alloy as in claim 4 which is abrasion and stress corrosion resistant and which has an ultimate tensile strength of at least 60 ksi and an electrical conductivity of at least 33 percent IACS. 

1.0 COBALT; FROM ABOUT 5 TO ABOUT 15 PERCENT ZINC AND, PREFERABLY, FROM ABOUT 7 TO ABOUT 13 PERCENT ZINC; PROVIDED THAT THE SUM OF THE IRON PLUS COBALT SHOULD BE FROM ABOUT 0.8 T AOUT 3.0 PERCENT AND PREFERABLY, FROM ABOUT 1.5 TO ABOUT 2.5 PERCENT.
 2. A copper base alloy as in claim 1 consisting essentially of about 1.0 to about 2.0 percent iron, about 0.3 to about 1.0 percent cobalt, about 7 to about 13 percent zinc, and the balance copper, provided that the sum of the iron plus cobalt contents shall be from about 1.5 to about 2.5 percent.
 3. A copper base alloy as in claim 2 containing less than 0.03 percent phosphorus.
 4. A copper base alloy as in claim 2 wherein said alloy is in the annealed condition.
 5. A copper base alloy as in claim 2 wherein said alloy is in the annealed and cold worked condition.
 6. A copper base alloy as in claim 4 which is abrasion and stress corrosion resistant and which has an ultimate tensile strength of at least 60 ksi and an electrical conductivity of at least 33 percent IACS. 